Abrasive article



Patented Sept. 2, i952 orrrcsi f ABRASIVE ARIQZQLE. .l ames-Ai Thomas,Jn, Niagara Falls; N. E, as- Signor to Thecarborundumscompany, Niagara iEallarN. Y., at corporation: of Delaware. AnplicationDecember 8,1949,1SeriaLNm131 855 9 Claims. 1

specifically to grinding wheels utilizing ametal;

bond f or diamond abrasive;

Qneobiect oi, 'thepresent "invention is to pro vide ametal-bondedabrasive wheel inwhiclrthe backing or supporting portion of the wheel-isrof ditfierent composition. from that, of the grinding portionsAnotherobiect oiitheinventionyis to r vid a me alebo ediabrasive wh e1-which will' b eresistant. to warping; distortion. dull ing sintering.Another 1 obj ectrof the present in-, vent onl sto make ame a bon ed briv :wheel which will. have; a. r hard, rigid metallic backing r,supportin port even; though sintering is carried out at comparatively:low temperatures; Stillj another 1objeetof the invention is :to provride a m t londed abras ve wheel meet nathe aforesaid obieots and whichcan 'be'obtained; over a. range oin Y selected bondhardness; Othen.objects pf; the invention will be perceived-L from-,the followingdescription thereon:

- Many; diamond abrasive-wheels-are so; con-i structed that the diamondabrasive isrcontained only in that portion ofthegwheel where cutting isdesiredawhile the -remainder; of the: wheel? is composed only of or verylargely of metal. In common practice the same metal is used for bondingthe cutting portion and the backing or' Such abrasive wheels are; cus'-c ing molded from metal powders alone or with small amounts of filleror lubricant and the cutting portion being molded from a mixtureof thesame metal powders and diamond abrasive, the two portions being thensintered into an integral body. The metal powders most generally used inthe making of sintered diamond abrasive articles are copper and tin, thetwo metalsbeing' usually combined in: proportions such assthose in.bronzei It has been found'that such metal bonded abrasive wheels havea-tendency-to distort or warpduring 'sintering: It "is" believed thatthe tendency to distort, particularly-in the case of wheels ofsubstantial thickness, is caused by-differential shrinkage occurring inthe backing; or support; As the-temperature is raised during sintering;the pressedmetal powder of thGWhBBl expands until thesinteringtemperature is reached; When sintering begins shrinkage ocours;with the tppofthe-wheel beingfree to shrink somewhat more thanthe-bottomthereof-since the bottom or-tne-wheer is.- durine sinter eran: tactwith' aplate or batandthe frictionbtweerr the; bottom of" thewheel andjtlre-batteif dsk'to retard shrinkage; Another; possible causeor tortion or warping in some cases-:is; the -difference" between theexpansion and contraction; of; the; backing 0r. support ofthe wheel;andof-thc'abrafsilfeportion thereof: This is aresult offithe faet thatthehabrasive port-ion andthe backingor supporting portion arenott'hesameeveri-thoughth same alloyisusedjsince the abrasive portion-has itscoeificient'ofe pa and shr n ge char acteristicst mod iiedby t p es nceofthe; straw; s1ve,.. x

According to. U. S. Patent App cation Seria No cater rfirec sprnza 46::bA b eK f -i Bal and Carl G. Rose, now U48: Bar ntrND, 215 5551521 it wasfound that grinding. w e s wh h we nracticalyfree. of distortion or.Warning; 1 beproducediithe.backing r supporting portion of. thewheeiwaswtormeclzirom a met l p deribr awmix ure otmetal-.powderswh cn produ ed"a simmerin temperaturesastron metalbodrw hri 011,131 ever; becomingsutficiently plastic. to; permit differential shrinkage. This resultwas: obtailllq l with'abrasive wheels in whichthe bond for the abrasivewas formed primarily from copper and tin powders, for examplebonds suchas-are dis-t closed in Boyer Patent No. 2,1-3FI-,329;'- issued NO-Jvember 22, 1938, by employing-iron--powelen-orav mixture of? about 80 9iron powdertogether:

with 8-1-8% copper powder;and"1-4-% tin -powder; These sintered powderedmetal compositions,

' when usedas the backing or supporting-portiom Qfsthe abrasive wheelirequire firing at emgt perature imthe neighborhood of 800 C". inor'der;to develop afsatisfactorily high sintered strength'i While such a firingtemperaturarequirement found to besuitable in. making;whjeels-; of aer'-. tain grade ofhardnessawhereinthe bond for the: abrasive portion ofthe wheel contained..l0%. oii less 0t :tin; it wasz iounditthat when: th-bond f the.abrasirerportionilof he Wh el con ained-thegreater i amountsof till' iilti'zhe. nei hhQlhfiqdz Qt. l5 201% n ededrorthetmaking; ofabrasive wheels.- having a harder gradathe fir n idlnllfiwi uhfiigi 800C21 causedLa bloating; or nufiine Uffi'thfiiih composition to apointflwherevthe bondtwasg not acceptable. Attemptsto overcome.thistdifliou ltg by firing the grinding rwheels at: lowertcmperan turesresulted-in an undesirable loweringrof the strength of thesupportingcenter ofirthewheelrto the-' point where the resulting;wheelrwass no longer useful-iormany applications; t i

In accordance with the present! invention it;

primarily from copper and tin powders containhas now been found thatsatisfactory grinding Wheels which are practically free of distortionpercentage of iron powder can be varied between about 50%"and'75% byweight, the percentage of copper powder varied between 20% and 40% byweight and the percentage of tin powder varied between and by weight. Ithas been further found that the tensile strength of the non-abrasivebackingor supporting portion of the wheel can be still further increasedby the incorporation of approximately 2% by weight of aphosphorous-copper powder in the composi-- tion of the sintered metalbacking or support.

The sintered metal compositions employed for the non-abrasive supportingportion of the grinding wheels in carrying out the present invention arefired at a temperature in the neighborhood of .650" C. withthedevelopment of highly satisfactorytensile strengths. Aphosphorous-copper alloy powder which has been found satisfactory isthat sold by the' Metals Disintegrating Company' of Elizabeth, NewJersey, as phos-copper No. MD8685 containing 7-9% phosphorous. Theaforesaid compositions produce the desired satisfactory results, namely,high strength,,freedom from distortion and warping, and development of.high strength at firing temperatures as low as 65020., when used in thenon-abrasive supportingicenters or backings of grinding wheels in whichthe bond for theabrasive is formed ing asj high as 20% tin, for example,bonds such as'are disclosed in Boyer Patent No; 2,137,329, issuedNovember 22, 1938.

'Table I below shows the physical test results obtained with sinteredmetal compositions composed of 200 mesh size iron powder, copperpowdery-tin powder and a phosphorous-copperalloy powder containing 7-9%phosphorous. The

. results'shown were obtained on 1 x /2" x A" test .bars molded at45,000 p. s. i. and sintered at Omission of the phosphorous-copper fromthe compositions set forth in Table I above results in a lowering of thetransverse strength by ap? proximately 5,000 pounds although itspresence appears to have no effect upon the shrinkage characteristics ofthe compositions.

One particular composition which has been found to be highlysatisfactory as the sintered metal backing or supporting portion of agrinding wheel where the bond for the abrasive portion is composed of82% copper powder and 18% tin powder, and which can be fired toadequately L highly sintered strength at a temperature of 650 C. iscomposed as follows:

Percent By Parts By Weight Weight 53.9 55 200 Mesh size Iron Powder. 35.3 36 Copper Powder.

8. 8 9 Tin Powder. V 2.0 2 Phos-Copper Powder (Containing a 79%phosphorous). I

able commercial types and should be comparatively pure to permitregulation of the extent of alloying by adjustment of the sinteringtemperature and time. Such metal powders are preferably of 200 mesh andfiner size.

The molding of a peripheral grinding wheel of the type shown in Figures1 and 2 in which a metal core or backing l0 surrounds an'arbor hole I2and has formed integrally therewith an abrasive rim H is shown inFigures 4,5, and 6. In Figure 4 a mold block or plunger I5 is pro- 6'50,C. for 1 hours. vided with a central pin or plug I! and a closely 1TABLE I Composition Q T ansverse Rockwell F R BY Welght Added Parts$553229 S trength Hardness I By Weight Of Iron Copper Tin Phos'copper 8512 3 2 0. 00 42, 000 68 '80 10 4 2 0. 06 48,200 71 75 20 5 z 0.10 48,80075 7o 24 0 2 0. 13 54, 000 71 05 2s 1 2 0. 17 as, 100 so e0 32 s 2 0. 2401,700 82 A study of the above table will show that the transversestrength is greatest in those compositionswhere the percentage of ironis between %and 75%, the percentage of copper is be- 05 twe'en 20% and40%, and the percentage of tin is between 5% and 10%. It is also notedthat the percent shrinkage increases as thepercentage of iron isdecreased. It was found that compositions containing less than 50% ironpowder were completely unsatisfactory because of excessive shrinkage.The presence of more than '75 iron with correspondingly lowerpercentages of copper and tin requires a firing in the neighborhood01180020. to develop-high strengtns, 1

fitting mold. ring [6. A mixture of iron, copper,

and tin powders in an amount calculatedto :bei

sufiicient tomake a wheel center of the desired thickness is then placedon plunger 15. in the. cavity formed by the ring l6 and'pin lland isspread evenly therein.

Upper mold plunger |5a is then put in place and consolidating pressurewhich may be-as high as 15,000 to 20,000 p. s. i. is applied to theplunger-s l5 and I5a. After this preliminary consolidation of thebacking or support there is placed around mold ring l6, as shown inFigure 5, an outer mold ring l9 and the mixture of diamond a ra ve aemia! r e nees e for th abra:

site rim. iss-pread; evenly; the. space. between plunger lfidhandnmoldjring i9; upn ri..rin 16111- is. then. inserted-into theassembly. in...such 'positiomthat ihwill operateto compress; the abrasive; mix.against' ring: it: and the. whole. mold. as.-se'mblyzis,againsubjectedtopressure. .Asshown in Eigure;.-6,. theabrasive, rimand the. backing: or

support arebrought.togetherainto lineas the mold is-closed and suitablepressure which may-in some: cases be. as much .as 50,000. to 75.000 p.s. i. ormore is then applied. Theefiect of this pressure is tocause-unification. of.--the. abrasive rim and the ime'tallic backing orsupporting portion :so-that the-pressedwheel may be. handledas anintegral bodwwithoutdanger of.;sep aration 1 :3 .there is, shown asectional view ofsra form of abrasive wheel which is intended forgrinding on the face or ,sides; Here the. cut,-

portion. 1 3;imolded :from ,a, .mixture of.- abrametal-or-resinoid-andmay-also, of course, be r:

of any desired shape or configuration with such provision forinstallation on a grinding machine or spindle as is necessary.

After removal from the mold, abrasive wheels made in accordance with thepresent invention may be sintered in any convenient or desired manner. Asimple and effective manner is by supporting the wheel on a bat or plateand placing it in a heated furnace having a reducing or non-oxidizingatmosphere. The wheel is kept in the furnace for the necessary period oftime to obtain thorough sintering, the hardness of the bond beingdetermined largely by the temperature at which the sintering is carriedout. This is well known in the art and the hardness may be regulated asdesired.

In the foregoing description abrasive wheels of the type shown inFigures 1 and 2 have been described as having a metal support or corewhich extends from the abrasive peripheral rim to the arbor hole. Itwill be realized that with large wheels the amount of metal in such aconstruction will be large and'accordingly the weight of the wheel willbe excessive. With large wheels, therefore, it will frequently bedesired to have the metal core or support extend inwardly from theabrasive rim only a relatively small distance, of the order of l to 18times the thickness of the abrasive rim depending on the size of thewheel, and to have the rest of the core or support formed from somelighter material such as a moldable plastic which can be attached in anysuitable manner to the metal support or which may be molded in situinside the metal supporting ring. Wheel constructions of this type areintended to be within the scope of the present invention since theadvantages of the present invention are inherent therein even though theentire support is not formed of metal.

The proportion of diamond employed in the abrasive rim of the wheel isnot critical and will vary with the purpose for which the wheel isintended. Other types of abrasives might be used instead of diamondsalthough it has been found that except in very rare cases the expense ofmetal abras ve uch 6 bonds, is not. warranted except; for-- an-expensive .;as1diam.ond. However, sot-tar as t .res t mention: isooneerriedi. it will be, on.- ratrve with and, it is. intended to,cover;- atria-sire whe l 'made withall ,typestor-abrasive,materials suchas a um na, silicon carbide, boron; carbide,

emery, titan umcarbide. and the like.

"hermore although the invention has; bee i desg ibed with particularref-erencetobonds-ob;-

ent;,. inventio n and that the. inVentionLma'y-lbe u iliz d in producingabrasivearticles otherthan wheels, It is not-intendeduthat the inventionshall-belimitedexcept lewiu claimsr reclaim: w i

l, A ,metal-bondedabras e a t e omprising a sintered abrasive portion:containinga minor proportion of diamond abrasive particles and a bondcomprising the sintered reaction product of a major proportion of copperpowder and tin powder in an amount up to about 20% of the weight of saidbond, and an integral, sintered, non-abrasive metal support for saidabrasive portion comprising in sintered form about 50- '70% iron powder,24-40% copper powder and 6-10% tin powder.

2. A metal-bonded abrasive article comprising a sintered abrasiveportion containing a minor proportion of diamond abrasive particles anda bond comprising the sintered reaction product of a major proportion ofcopper powder and tin powder in an amount up to about 20% of the weightof said bond, and an integral, sintered, non-abrasive metal support forsaid abrasive portion comprising in sintered form about 50-80% ironpowder, 16-40% copper powder, 4-10% tin powder and containingapproximately 2% by weight of the bond of phosphorous-copper.

3. A metal-bonded abrasive article comprising a sintered abrasiveportion containing a minor proportion of abrasive particles and a bondcomprising the sintered reaction product of a major proportion of copperpowder and tin powder in an amount up to about 20% of the weight of saidbond, and an integral, sintered, non-abras1ve metal support for saidabrasive portion comprising in sintered form about 50-70% iron powder,24-40% copper powder and 6-10% tin powder.

4. A metal-bonded abrasive article comprising a sintered abrasiveportion containing a minor proportion of abrasive particles and a bondcomprising the sintered reaction product of a major proportion of copperpowder and tin powder in an amount up to about 20% of the weight of saidbond, and an integral, sintered, non-abrasive metal support for saidabrasive portion comprising in sintered form about 50-80% iron powder,16-40% copper powder, 4-l0% tin powder and containing approximately 2%by weight of the bond of phosphorous-copper.

by; the scope of the 01.:-

5. A metal-bonded abrasive article comprising a" sintered abrasiveportion containing a minor proportion of diamond abrasive particles anda bond comprising a sintered reaction product of a majorproportion ofcopper powder and tin powder in :an amount up to about 20% of the weightof said bond,- and an integral, sintered, nonabrasive metal support forsaid abrasive portion comprising in sintered form about 54% iron powder,35% copper powder, 9% tin powder and 2% phosphorous-copper powder. Y

6. A metal-bonded abrasive article comprising a sintered abrasivevportion containing a minor proportion Ofdiamond abrasive particles anda bon'd comprising the sintered reaction product of a major proportionof copper powder and tin powderinanamou'nt up to about 20% of the weightof said bond, and an integral, sintered, non-abrasive metalsupport forsaid abrasive por- ;tion comprising in sintered form about 55 iron.powder,:36% copper' powder and 9% tin powder.

71 A metal-bonded abrasive article comprising a sinteredrabrasiveportion containing a minor proportion'of abrasive particles and a bondcomprisingthesintered reaction product of a major proportion of copperpowder and tin powder in anamountup to about 20% of the weight of saidbond,- and :an integral, sintered, non-abrasive metal support for saidabrasive portion comprising in sintered form about 54% iron powder, 35%copper powder, 9% tin powder and 2% phosphorous-copper powder.

- 8. A metal-bonded abrasive article'comprisi ng a sintered abrasiveportion containing ar min'or proportion of diamond abrasive particlesand a bond comprising th sintered reaction product of approximately 82%copper powder'and 18%; tin

of the bond of phosphorous-copper. -:i r

' JAMES A. TnoMAs, R.

, REFERENCES CITED' 7 The following references are of record ,inthe fileof this patent: j

a UNITED STATES PATENTS I 1 Number Name Date 2,506,556 Ball et al. May2,1950

derrand containing approximately 2% .byweight

1. A METAL-BONDED ABRASIVE ARTICLE COMPRISING A SINTERED ABRASIVEPORTION CONTAININNG A MINOR PROPORTION OF DIAMOND ABRASIVE PARTICLES ANDA BOND COMPRISING THE SINTERED REACTION PRODUCT OF A MAJOR PROPORTION OFCOPPER POWDER AND TIN POWDER IN AN AMOUNT UP TO ABOUT 20% OOF THE WEIGHTOF SAID BOND, AND AN INTERGRAL, SINTERED NON-ABRASIVE METAL SUPPORT FORSAID ABRASIVE PORTION COMPRISING IN SINTERED FORM ABOUT 5070% IRONPOWDER, 24-40% COPPER POWDER AND 6-10% TIN POWDER.